"For this is good and acceptable to God our Savior, who desires all men to be saved and to come to the knowledge of the truth" (1 Timothy 2:3-4). God desires all to be saved from death, judgment, and everlasting punishment. God sent His Son into the world to make the one and only sacrifice which is sufficient to save all (John 12:32; 1 John 2:2). Then, why are all not saved?
Not all will come to "the knowledge of the truth" (1 Timothy 2:4). Jesus said, "I am the truth" (John 14:6). The Spirit of truth uses the word of truth to bring us to the one who is the truth (John 16:13; 17:17). God will not save anyone who rejects the truth. Those who reject the truth, believe the lie. They perish, "because they did not receive the love of the truth, that they might be saved" (2 Thessalonians 2:10).
Not all will trust in Christ. None who sincerely trust in Christ will be turned away (John 6:37). No one who believes in Him will be disappointed (Romans 10:11). God's call to salvation is for all nations, Jew and Gentile (Romans 1:16; Acts 1:8). The gospel of Christ is freely offered to all.
Not all will repent and believe on the Lord Jesus Christ (Acts 16:31; 17:30). This speaks of our responsibility. Those who refuse to repent and believe on the Lord Jesus Christ are responsible for their own just condemnation (Luke 13:3, 5). All who repent and believe the gospel of Jesus Christ will be saved (John 3:36; Acts 2:37-39).